Plural channel system wherein the input signals are unaltered if within standard limits, but are averaged, if outside limits

ABSTRACT

A control apparatus has redundant input signals from which an output signal is produced. In part it comprises three inputs to which the respective input signals are applied and three outputs. There are three resistors of known value with each connecting a respective input and a respective output. There are six resistance devices each connecting a respective input with one of the remaining outputs between which there is not one of the resistors. The resistance devices comprise a voltage sensitive double-pole whose resistance substantially equals said known value below a selected threshold voltage but which becomes very great above said threshold voltage. The threshold voltage is selected to be sufficiently greater than the normal input voltage to represent a malfunction situation.

United States Patent Matejka [451 Oct. 10,1972

1541 ILURAL CHANNEL SYSTEM WHEREIN THE INPUT SIGNALS ARE UNALTERED IFWITHIN STANDARD LIMITS, BUT ARE AVERAGED, IF OUTSIDE LIMITS [72]lnventor: Edgar Matejka, Singen/Hohentwiel,

Germany [73] Assignee: Bodenseewerk Geratetechnik GmbH,Uberlingen/Bodensee, Germany [22] Filed: Dec. 15, 1970 [21] Appl. N0.:98,364

[30] Foreign Application Priority Data Dec. 17, 1969 Germany ..P 19 63130.2 Nov. 10, 1970 Germany ..P 20 55 084.9

[52] US. Cl. ..307/219, 307/237, 307/304,

[51] Int. Cl ..G06f 11/08, G08b 29/00, H03k 5/08 [58] Field of Search..307/204, 219, 235, 251, 237, 307/279, 304', 328/116, 117, 137, 139,147,

3,492,588 1/1970 Woodward, Jr. ..307/219 X 3,521,087 7/1970 Lombardi..307/237 X 3,369,129 2/1968 Wolterman ..307/237 3,243,585 3/1966Escobosa ..328/152 X 3,333,180 7/1967 Neu ..307/304 X 3,551,824 12/1970Rotier ..328/147 Primary ExaminerHerman Karl Saalbach AssistantExaminer-L. N. Anagnos Att0rney-Darbo, Robertson & Vandenburgh 5 7]ABSTRACT A control apparatus has redundant input signals from which anoutput signal is produced. In part it comprises three inputs to whichthe respective input signals are applied and three outputs. There arethree resistors of known value with each connecting a respective inputand a respective output. There are six resistance devices eachconnecting a respective input with one of the remaining outputs betweenwhich there is not one of the resistors. The resistance devices comprisea voltage sensitive double-pole whose resistance substantially equalssaid known value below a selected threshold voltage but which becomesvery great above said threshold voltage. The threshold voltage isselected to be sufficiently greater than the normal input voltage torepresent a malfunction situation.

[56] References Clted 11 Claims, 10 Drawing Figures UNITED STATESPATENTS 3,489,889 l/l970 Escobosa ..244/77 M X 1 &

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IINVENTOR PLURAL CHANNEL SYSTEM WI-IEREIN THE INPUT SIGNALS AREUNALTERED IF WITHIN BACKGROUND AND SUMMARY OF THE INVENTION Thisinvention relates to a circuit arrangement for forming the mean value ofseveral input voltages, in

which the input voltages are applied through resistor branches to acommon load resistor at which the mean value output voltage appears, andin which at least a part of the resistor branches is controlled independence on the difference between the output voltage at the loadresistor and the respective input voltage in such a manner that thisinput voltage will be suppressed, if it deviates by more than a givenextent from the output voltage.

More specifically, this invention relates to a circuit arrangement forsynchronizing signals in redundant systems comprising a plurality ofsignal inputs and a plurality of signal outputs, in which each signalinput is connected with all of the signal outputs through one resistorbranch each.

Circuit arrangements of the type indicated are required in apparatus, inwhich for reasons of safety, measured value transmitters and signalchannels are provided in multiple number; for instance, in automaticpilots in which one and the same control signal is generated by threesignal circuits independent of each other. Due to tolerances of thecomponents used, these signals always show slight signal differences.These signal differences which are not due to shortcomings of thecomponents complicate an error recognition by monitoring devices. Anerror is considered to exist if the signal differences exceed apre-established fixed value. It may therefore be expedient within amultiplied signal chain to evaluate the signals once or several times.In prior art arrangements (for example, see Ser. No. 858,737, filedSept. 17, 1969, entitled SIGNAL SELECTION CIRCUIT, the disclosure ofwhich is incorporated by reference) this is accomplished by circuitswhich select from three input signals the signal of the mean amplitude,thus, of the amplitude having a magnitude between that of the two othersignals. As these circuits, however, automatically suppress an errorsignal, they must be equipped with additional arrangements for errorrecognition so that an error, if it occurs, does not remain concealed.These additional arrangements for error recognition require quite aconsiderable amount of apparatus.

Moreover, there are prior art circuit arrangements in which a mean valueis formed from several input voltages (in the meaning of an arithmeticmean). The input voltages are applied through resistor branches to acommon load resistor across which the mean value output voltage appears.In this connection, provisions are made that each of the resistorbranches is controlled in dependence on the difference between theoutput voltage at the load resistor and the associated input voltage insuch a manner that a particular input voltage will be suppressed if itdeviates by more than a given extent from the output voltage. This givenextent corresponds to the signal tolerances. A signal which deviates bymore than this given extent from the mean value, is considered as anerror signal and is suppressed.

It is an object of this invention to provide a circuit arrangement forforming the mean value of several input voltages, in which inputvoltages which deviate by more than a given extent from the outputvoltage, are suppressed.

It is another object of this invention to effect such a suppression ofthe out of place input voltages in a contactless manner.

It is an object of this invention to provide a circuit arrangement forsynchronizing, thus equalizing several signals, in which such asynchronization is effected so long as the signal deviations of severalsignals (deviations within the range of permissible tolerances) do notexceed a pre-established fixed value, but a signal whose deviationexceeds the fixed value of the permissible tolerances is transferred asunfalsified as possible. With such a circuit arrangement forsynchronization it is then possible to restrict the signal monitoring toa few points in the signal flux, thereby leading to a substantial savingof components.

According to this invention, provision is therefore made that thevoltage-controlled resistor branches include voltage-sensitivedouble-poles whose resistance becomes very great above a voltagethreshold.

In a further modification of this invention a synchronizing circuit ofthe type mentioned in the beginning is designed in such a manner thateach signal input is connected with an associated signal output througha voltage insensitive resistor and with all of the other signal outputsthrough voltage sensitive doublepoles whose resistance values below athreshold value of the voltage applied thereto are equal to the saidvoltage in-sensitive resistor and above this threshold value become verygreat.

DESCRIPTION OF THE DRAWINGS FIG. 1 shows the application of n inputsignals to an output.

FIG. 2 shows the characteristic of the double-poles used in the circuitof FIG. 1.

FIG. 3 shows a complete circuit arrangement for three input signals andthree output signals.

FIGS. 4a to 40 show the three output voltages in dependence on one inputvoltage.

FIG. 5 illustrates one embodied form of a doublepole applicable to theinvention.

FIG. 6 illustrates another embodied form of a double-pole.

FIG. 7 illustrates a third embodied form of a doublepole.

FIG. 8 shows the characteristic of a cold conductor for use with theinvention.

DESCRIPTION OF SPECIFIC EMBODIMENTS The following disclosure is offeredfor public dissemination in return for the grant of a patent. Althoughit is detailed to ensure adequacy and aid understanding, this is notintended to prejudice that purpose of a patent which is to cover eachnew inventive concept therein no matter how others may later disguise itby variations in form or additions or further improvements. The claimsat the end hereof are intended as the chief aid toward this purpose, asit is these that meet the requirement of pointing out the parts,improvements, or combinations in which the inventive concepts are found.

FIG. I shows the used basic circuit for n input signals. An input signalU, is applied at input E and transferred to output A through branchresistor R. Similarly, the inputsE, E, receive input signals U, U, whichgo to the common output A through voltage sensitive double-poles Z, Z,,.In order that the operation of the illustrated basic circuit isfunctionally correct, the double-poles must have the characteristicillustrated in FIG. 2. The characteristic shows that the double-polesarc voltage sensitive. For a voltage applied across the double-pole, thedouble-pole resistance shall be For a voltage applied across thedouble-pole, however, the current through the double pole shall belimited to the value The double-pole voltage U, is selected inaccordance with the permissible signal deviation A U of the inputvoltages. For the current L, it applies that the current must be greaterthan the required maximum output current of the circuit arrangement.From these data, the (FIG. 1) resistance ri/ o is calculated.

FIG. 3 illustrates a complete circuit arrangement for three inputsignals U U and U and three output signals U U and U In this case, thebasic circuit illustrated in FIG. 1 is provided with three inputs E,, E,and E and is used three times to obtain three outputs A,, A, and A,.There is a resistor R connecting each input with a respective output.The connections between the remaining inputs and outputs is provided byvoltage sensitive double-poles Z.

In FIGS. 4a, 4b and 4c the three output voltages U U,,, and U areillustrated in dependence on an excessive input voltage U,. It wasdetermined that up to the signal deviation A U, the double-poles havethe resistance R. From this condition U is obtained. Under the conditionU A U, U,= U 0 U,,= 2/3 A U Forninputs A U,=(N-l/n)'A U is obtained.

FIGS. 4a to 4c show that the output signals of the circuit arrangementare identical up to a signal deviation of A U. If the signal deviationexceeds the value A U at the input E, (FIG. 3), then the output signalsU and U will no longer be influenced by it (FIGS. 4b and 4c). Themaximum signal deviation at the outputs A, and A, based'on the signaldeviation at the input E is A U/ 3. At the output A, appears the voltage2 A U/ 3 up to a value of U =2 A U, whereas signal deviations beyondthat and reduced by the constant value 2 U, become fully effective atthe output A,. Since the circuit regarding input and associated outputis always designed identically, the identical results are obtained forthe two other inputs.

The preceding considerations were made without a load. The permissibleload current is maximally I It effects an output signal offset bymaximally 0.5 U, at the outputs for an input signal deviation smallerthan A U. For input signal deviations greater than A U (in the case ofan error signal), it effects an output signal offset by maximally UThus, the following situation is ob tained:

As long as the signal deviations are below a preestablished thresholdvalue (hence, are due to the permissible tolerances of the components),a mean value formation is effected so that at all of the three signaloutputs the same signals occur and can be processed further in thesucceeding channels. If a signal is out of place", i.e. exceeds thepermissible tolerance, this signal will become fully effective at arespective one of the outputs, apart from a certain shift in amplitude,while being suppressed as an error signal at all other outputs. Thus, atthe latter outputs the error signal is discounted and a mean valueformation is effected so that in these channels identical signals withinthe permissible tolerances can be processed. In the channel of saidrespective one output the error signal occurs. This error signal becomeseffective in a similar manner also in the succeeding synchronizingcircuits. Thus it is possible to provide an arrangement for errorrecognition at a specific point of the signal channels and to eliminatethe error signal at the same time. However, it is not necessary toprovide such an arrangement for error recognition in each individualsynchronizing circuit.

The voltage sensitive double-poles (e.g. Z of FIG. 3) are obtainablefrom the following components:

1. Cold Conductors See FIG. 8. A cold conductor is atemperature-dependent resistor which is of very low resistance below theCurie-temperature and has a high positive temperature coefficient abovethe Curie-temperature. The resistance of a cold conductor can be variedby means of the current flowing therethrough. As the variation inresistance is effected via the by-pass of temperature, also the ambienttemperature influences the break of the characteristic. It is thereforethat a stabilization of the ambient temperature be provided. In order tobe able to adjust the magnitude of the resistance of the double-pole tothe necessary value, a balancing resistor must be connected in serieswith the cold conductor.

2. Circuit Arrangements with Field Efi'ect Transistors The circuitillustrated in FIG. 5 employs a symmetrical field effect transistor FT]as the main component of a voltage-sensitive double-pole such as mightbe used in each resistor branch Z. The symmetrical field effecttransistor has a pair of preceding and succeeding resistors R Its baseis connected through diodes D,, D, with the free end of the resistors. Abalancing resistor R, is in series-connection in this circuit to make upthe remainder of the total resistance R. This double-pole circuit alsohas the necessary characteristic. Herein, the low resistance range issubstantially determined by the properties of the field effecttransistor Fll. To make up the required resistance R, the balancingresistor R A is used. The adjustment of the current limitation I, isaccomplished by means of the resistors R Advantageously, field effecttransistors with low drainsource resistance (r and small pinch-offvoltage are used.

Another circuit including field effect transistors is shown in FIG. 6,in which the double-pole of each resistor branch Z comprises a pair offield effect transistors (FT2, Fl3) connected back-to-back(antiparallelly) by resistors R The grid of each field effect transistoris connected through a resistor R with the cathode of the othertransistor. A balancing resistor R, is arranged in series-connection inthis circuit to make up the total resistance R. Herein, the current I isadjusted with the resistors R the resistance R with the resistor R 3.Circuits with Operational Amplifiers If very accurate values for R andI, are to be provided, the use of four-pole circuits, the transfercharacteristic of which corresponds to that of the doublepoles, arerecommended. In these circuits, operational amplifiers are preferablyused. An example for such a circuit to form a resistor branch is shownin FIG. 7. Utilizing a field effect transistor double-pole of the typediscussed in connection with FIG. 5, its input is connected to theoutput of an operational amplifier V. The output P of the double-pole isconnected to the input of the amplifier by a feedback resistor Rproviding negative feedbacks. The branch input E is connected by aresistor to the amplifier input by a resistor R The branch output A isconnected to P by a resistor R, which serves to make up the desiredtotal resistance R. The FIG. 5 double-pole (FTl, R R,-, D, and Dprovides current limiting in the series circuit between input E andoutput A.

Of course, also other circuit arrangements are known which can be usedherein to provide current limitation, a condition being that the currentlimitation is effective in a bipolar manner. The negative feedback ofthe amplifier according to the current limiting circuit is derived atthe point P and is applied via the feedback resistor R to the invertingpoint (input) of the amplifier. The input signal U is also applied tothe non inverting point via the input resistor R Due to the negativefeedback the source impedance is very small and can be neglected, whenthe amplifier is operated on its characteristic. Then, the sourceimpedance at the output point A of the arrangement is determined only bythe resistance R, which connects the point P with the point A.Therewith, the resistance R A can be selected in accordance with therequirements of the circuit arrangement of the invention and generallycorresponds to the resistance R.

It may also be mentioned that the wiring of the operational amplifiercan substantially be selected as desired. Thus, special frequencycharacteristics also can be achieved.

I claim:

1. In an apparatus for forming the mean value of several input voltagesin synchronizing signals in redundant systems including a plurality ofsystem inputs and a plurality of system outputs, and a plurality ofbranches each having an individual input and having a common output withresistor means in each branch, there being one of said branches betweeneach system input and each system output respectively, the improvementcomprising:

a first of the branches connected to each one of the system inputshaving a said resistor means comprising a voltage insensitive resistorof a given magnitude, each said first branch connecting a respectivesystem input with a respective system output, the remaining branchesconnected to each system output each comprising a voltage sensitivedouble-pole whose resistance value becomes very great above apredetermined voltage threshold and below said voltage threshold issubstantially equal to said given magnitude.

2. In an apparatus as set forth in claim 1, wherein each voltagesensitive double-pole includes a field effect transistor having threeconnections a first of which is a base connection, a diode and aresistor connected in series between the first and a second of thetransistor connections with a first juncture therebetween, a diode and aresistor connected in series between the first and a third of thetransistor connections with a second juncture therebetween, a balancingresistor, said junctures and said balancing resistor being connected inseries between the branch output and the branch input.

3. Inan apparatus as set forth in claim 2 including an operationalamplifier having an input and an output connected in the series circuitbetween the branch input and output, the amplifier output beingconnected to the first juncture, a negative feedback circuit including aresistor connecting the second juncture with the amplifier input, andv aresistor connecting the amplifier input to the branch input.

4. In an apparatus as set forth in claim 1, wherein each voltagesensitive double-pole includes a pair of field effect transistorsconnected back-to-back by a pair of resistors and in series with abalancing resistor between the branch input and the branch output.

5. In an apparatus as set forth in claim 1, wherein the double-poleincludes a cold conductor.

6. In an apparatus for forming the mean value of several input voltagesand comprising a plurality of signal inputs, a common signal output,resistor means connected between each of said signal inputs and saidcommon signal output and having a substantially linear resistancecharacteristic in the normal operating range, and a load resistorconnected to said common output, whereby the signal obtained at saidcommon signal out put under normal operating conditions is proportionalto the arithmetic mean value of said input voltages, the improvementcomprising:

at least all but one of said resistor means having a voltage sensitiveover-all resistance, which becomes very large above a predeterminedvoltage threshold defined by the upper end of said normal operatingrange.

7. In an apparatus as set forth in claim 6, wherein said all but one ofsaid resistor means is a voltage sensitive double pole.

8. In an apparatus as set forth in claim 7, wherein each voltagesensitive double-pole includes a field effect transistor having threeconnections a first of which is a base connection, a diode and aresistor connected in series between the first and a second of thetransistor connections with a first juncture therebetween, a diode and aresistor connected in series between the first and a third of thetransistor connections with a second juncture therebetween, a balancingresistor, said junctures and said balancing resistor being connected inseries between the branch output and the branch input.

10. in an apparatus as set forth in claim 7, wherein each voltagesensitive double-pole includes a pair of field effect transistorsconnected back-to-back by a pair of resistors and in series with abalancing resistor between the branch input and the branch output.

11. in an apparatus as set forth in claim 7, wherein the double-poleincludes a cold conductor.

# I i i

1. In an apparatus for forming the mean value of several input voltagesin synchronizing signals in redundant systems including a plurality ofsystem inputs and a plurality of system outputs, and a plurality ofbranches each having an individual input and having a common output withresistor means in each branch, there being one of said branches betweeneach system input and each system output respectively, the improvementcomprising: a first of the branches connected to each one of the systeminputs having a said resistor means comprising a voltage insensitiveresistor of a given magnitude, each said first branch connecting arespective system input with a respective system output, the remainingbranches connected to each system output each comprising a voltagesensitive double-pole whose resistance value becomes very great above apredetermined voltage threshold and below said voltage threshold issubstantially equal to said given magnitude.
 2. In an apparatus as setforth in claim 1, wherein each voltage sensitive double-pole includes afield effect transistor having three connections a first of which is abase connection, a diode and a resistor connected in series between thefirst and a second of the transistor connections with a first juncturetherebetween, a diode and a resistor connected in series between thefirst and a third of the transistor connections with a second juncturetherebetween, a balancing resistor, said junctures and said balancingresistor being connected in series between the branch output and thebranch input.
 3. In an apparatus as set forth in claim 2 including anoperational amplifier having an input and an output connected in theseries circuit between the branch input and output, the amplifier outputbeing connected to the first juncture, a negative feedback circuitincluding a resistor connecting the second juncture with the amplifierinput, and a resistor connecting the amplifier input to the branchinput.
 4. In an apparatus as set forth in claim 1, wherein each voltagesensitive double-pole includes a pair of field effect transistorsconNected back-to-back by a pair of resistors and in series with abalancing resistor between the branch input and the branch output.
 5. Inan apparatus as set forth in claim 1, wherein the double-pole includes acold conductor.
 6. In an apparatus for forming the mean value of severalinput voltages and comprising a plurality of signal inputs, a commonsignal output, resistor means connected between each of said signalinputs and said common signal output and having a substantially linearresistance characteristic in the normal operating range, and a loadresistor connected to said common output, whereby the signal obtained atsaid common signal output under normal operating conditions isproportional to the arithmetic mean value of said input voltages, theimprovement comprising: at least all but one of said resistor meanshaving a voltage sensitive over-all resistance, which becomes very largeabove a predetermined voltage threshold defined by the upper end of saidnormal operating range.
 7. In an apparatus as set forth in claim 6,wherein said all but one of said resistor means is a voltage sensitivedouble pole.
 8. In an apparatus as set forth in claim 7, wherein eachvoltage sensitive double-pole includes a field effect transistor havingthree connections a first of which is a base connection, a diode and aresistor connected in series between the first and a second of thetransistor connections with a first juncture therebetween, a diode and aresistor connected in series between the first and a third of thetransistor connections with a second juncture therebetween, a balancingresistor, said junctures and said balancing resistor being connected inseries between the branch output and the branch input.
 9. In anapparatus as set forth in claim 8 including an operational amplifierhaving an input and an output connected in the series circuit betweenthe branch input and output, the amplifier output being connected to thefirst juncture, a negative feedback circuit including a resistorconnecting the second juncture with the amplifier input, and a resistorconnecting the amplifier input to the branch input.
 10. In an apparatusas set forth in claim 7, wherein each voltage sensitive double-poleincludes a pair of field effect transistors connected back-to-back by apair of resistors and in series with a balancing resistor between thebranch input and the branch output.
 11. In an apparatus as set forth inclaim 7, wherein the double-pole includes a cold conductor.